At the end of a snow storm, Caleb saw there was a lot of snow on his front lawn. The temperature increased and the snow began to melt at a steady rate. The depth of snow on Caleb's lawn, in inches, can be modeled by the equation S=-2t+18,S=−2t+18, where tt is the time, in hours, after the snow stopped falling. What is the yy-intercept of the equation and what is its interpretation in the context of the problem?